all qualified names are inspected, whether a namespace uri is defined,
for these uris the prefix and uri is returned. This arrow is useful for
namespace cleanup, e.g. for documents generated with XSLT. It can be used
together with collectNamespaceDecl to cleanupNamespaces

generate unique namespaces and add all namespace declarations to all top nodes containing a namespace declaration
Usually the top node containing namespace declarations is the root node, but this isn't mandatory.